In the state of the art for engine design it is a desirable objective to design an adiabatic engine in which all of the thermal energy developed by the combusted fuel is utilitzed and recovered as useful work. While thermal losses are inevitable, by maximazing the recoverable energy thermal efficiencies approximating 85% can be achieved. However, in order to achieve such efficiencies extraordinarily high temperatures and pressures must be developed. By using appropriate supercharging means, such as the positive displacement devices described in U.S. Pat. No. 4,791,787, issued Dec. 20, 1988 and filed Dec. 5, 1985, entitled Regenerative Thermal Engine engine pressures approaching 300 bars and temperatures of approximately 2,400 degrees Farenheit can be obtained. Designing combustion chambers and reciprocator components to withstand such temperatures and pressures becomes a formidable task, particularly where thermal energy is desired to be converted into useful work and not dissipated by bulky and wasteful cooling systems. Where the engines are designed for military use, the waste heat dissipated by cooling systems or direct exhaust results in a high infrared signature which is readily detectable.
The principle problem confronting engine designers, therefore, is to devise a high tempertature and pressure engine that develops a high power density wherein the engine is adapted to use a high supercharging level without the penalty of low compression ratio which is a main factor in reducing efficiency.
While various advances in achieving the objective of an adiabatic engine have been made utilizing ceramics, many unsolved problems arise with the adaptation of ceramics, which have desirably high heat resistant characteristics, to reciprocal engines that require high strength in its stationary and dynamic components as well. In addition to strength, the other common problem in utilizing ceramics is the dissimilarity in the expansion coefficient of ceramic components in comparison with conventional metallic components with which they must be associated.
This invention is directed at solving many of the problems in adapting ceramic components to a high pressure, high temperature reciprocal engine that includes various heat recovery subsystems for producing a compact high power density engine having a minimal heat dissipation. The engine is particularly suitable for military applications where it is desirable to have a small power package located under armoured protection with minimal detection heat radiation. In this manner the payload, weaponry, fire capacity, fuel, electronics or other components of the vehicle can be enhanced with the reduction in size and weight of the power plant.